This is I said '(2)' problem. They choose lane with Dynamic selection look no work good. And don't spawn, you can check look road 'Green Arrow' on map edge, when use this function, after series seconds, the vehicles will not spawn and if you use 'Clear Traffic' from toolbar, and vehicles will spawn series seconds and go back not spawn.

And there are two reasons, one the "Dynamic lane selection" just set like that, and two it's a problem. And if mod original set like that, it got good reason for reduce all vehicles number and reduce performance.

And it's working when you got new house and citizen can move in from road 'Green Arrow' on map edge.

Points to confirm:
Are you loading old save (I belive) or creating new game?
Do you have Advanced Vehicle AI activated in settings?
Green arrow, you mean outside connections? (I've to check in-game)
Could you post that save to any of file share services? Would be great

Yep, I do all test with start a new game. It activated and yes outside connections.

You can do the simple test, start a new game, and only activated it, then watch outside connections, you will see that.

I've noticed that citizens spawned outside map and came to city only after almost all houses were built